Gunmen from across the Rio Grande fired at U.S. law enforcement, instigating the second cross-border gunfire exchange this month, Rio Grande Valley news outlets said Monday. No injuries were reported from the brief gun battle, which broke out Sunday morning after police chased a truck loaded with marijuana.

The smugglers threw bundles of drugs at them, then drove into the Rio Grande and splashed back to Mexico. Police fired back in response to shots from the other side.Mission Police Chief Leo Longoria told The Monitor in McAllen a woman who drove a second vehicle toward police during the pursuit could...